The protection of crops from weeds and other vegetation which inhibit crop growth is a constantly recurring problem in agriculture. To help combat this problem, researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use.
In some cases, herbicidal active ingredients have been shown to be more effective in combination than when applied individually and this is referred to as “synergism.” As described in the Herbicide Handbook of the Weed Science Society of America, Ninth Edition, 2007, p. 429, “‘synergism’ [is] an interaction of two or more factors such that the effect when combined is greater than the predicted effect based on the response to each factor applied separately.” The present invention is based on the discovery that (a) propyzamide and (b) aminopyralid, already known individually for their herbicidal efficacy, display a synergistic effect when applied in combination.
Propyzamide, 3,5-dichloro-N-(1,1-dimethylpropynyl)benzamide, is an amide herbicide. It is described in The Pesticide Manual, Fourteenth Edition, 2006. Propyzamide is applied either pre-emergence or early post-emergence to provide selective control of many annual and perennial grasses and some broadleaf weeds in a variety of crops.
Aminopyralid, 4-amino-3,6-dichloro-2-pyridinecarboxylic acid, is a picolinic acid or pyridine herbicide. It is described in The Pesticide Manual, Fourteenth Edition, 2006. Aminopyralid is used for long-term control of annual and perennial broadleaf weeds in grassland, pastures, some crops and industrial vegetation management.